All Blacks lock Ali Williams has been ruled out for eight weeks due to a knee injury.

The Blues second-row will consult a surgeon in Auckland later this week to correct the problem before a lengthy lay-off.

Williams has been troubled by injuries in recent seasons and had corrective surgery in the same knee, albeit for a separate issue, prior to the current Super Rugby campaign.

"Ali developed a sore right knee over the last couple of weeks and a scan has revealed that he has a flap of loose articular cartilage which will require surgery. He will see a surgeon this week in Auckland," All Blacks doctor Deb Robinson said.

"It's obviously disappointing for Ali to have this new injury but he is expected to make a full recovery. Once he has had the surgery, we will have a clearer idea of how long he will be out of rugby but it he is expected to be out for a minimum of eight weeks."

All Blacks boss Steve Hansen has drafted in Chiefs flanker Liam Messam as cover for Williams in his squad to face Ireland next weekend.